System for policing vehicles in traffic



Dec. 20, 1938. D; E, MAR ALL 2,140,918

SYSTEM FOR POLICING VEHICLES- IN TRAFFIC Filed Dec. 7, 1935 Jpe'p' 0007-0081 A? Jw/htb 36 /.9 r 56 5 ea c0550 1 1 INVENTOR. c .34.00/70/05/70/1960/6 .39. 35 27 BY 4 36M A M W 374; ATTORNEY L/4 Patented1938 PATENT OFFICE l SYSTEM son mama vnmcms In @Dona Id- E. Marshall,Pains vascular, Cali!- j Application December 1, 1935, Serial No. 53,332a 8 Claims. (01. 117411.52

. -My inventionrelates toimeans for indicating the speed-oi a vehicleand isparticularly adapted to indicate thespeed at alocation remote fromthe moving vehicle. The invention is of especial utility in connectionwithautomotive vehicles, in which case the speed may be indicated onanother vehicle, for instance, that of. a patroliingpolice oilicer. 1Thus my invention" provides an eiiicient means for locating violators oithe speed laws as 10 well asiordete'rmining the vapproximate speed atwhich they are traveling.

It is an object of my invention to provide a;

means and methodwherebythespeed of a vel hiclemaybe indicated at a pointremote from i and unconnec ed with the moving vehicle.

Another object of the invention is to provide means fortransmittingirorn a 'moving vehicle electromagnetic or radio signalhaving some characteristic determined by'the speed of the a l vehicle,and means for receiving at some remote 1 point the transmitted radiosignal and, determining thereiromthe speed of r the vehicle from whichthe signalemanates. For eirample, in one practice oi. the invention Lnay provide the vehicle with a radio transmitter adjusted to deliver acarrier wave ata predetermined frequency, this n i l transmitterhavingsarneans for modulating the v *carrie'rwave to diflerent soundfrequencies in accordance withthe speed atwhich thev vehicle 301.!travelling.'

Another object is to provide means for sending from a moving vehicleamodulated-radio wave;

ql'having a -irequency determined by the speed of i tha vehicle and:meansiorselectively receiving thesefvaried -irequency wavesat someremote point {to determine the corresponding speed. Y Still'anotherobject of my inven tion is to provide a means of varying the frequencyof a transinitted radiowave inrres ponse' to the speed of a 40 vehicle,which means may beemployed in con- -t nection with a speedometeroperating on the P1111? ciple of those now in common use.

These and otherobjects I attain in amanner which will be clear from aconsideration of the followingdescription taken in connection with theaccompanying drawing, of which:

Fig. 1 is a diagram oi'tthe electrical, circuit employedin transmittingthe speed-controlled sig.-

nal from a moving vehicle. a

60 i Fig. 2 is adiagram'oi the electrical circuit emthe moving vehicle,e I l Fig. 3 is a diagram oi an alternative electrical circuit employedin transmitting the speed-con v Y other winding 24 of transformer 23 isa condenser 55 ll trolled signal irom a moving vehicle.

ployed in receiving the signal transmitted irom ,vehicle. I haveillustrated my invention in the form wherein I vary the carrierfrequency of the 5 transmited wave in response to speed'oi the vehicle.In this form I choose aplurality of consecutive speed ranges andtransmit a modulated radio wave having a radiovrfrequency dinerent foreach speed range.

The electrical circuit employed for this purpose is shown inFig 1'. Avacuum tube II, which i may be a type "30 triode tube is employed asoscillator. The plate or anode of this tube'is, connected-throughblocking condenser H, which 15 may have a capacity of .002 microiarad,and wire I! to one side; of: the oscillating circuit. Thegrid of-tube l0 is also connected to the oscillating circuit by'wire llthroughcondenser il which may have a capacity oi .00025 microiarad and which is20 shunted by resistor-ii having a resistance oi about 10,000 ohms. -Theoscillating circuit comprises an inductance". and a condenser connectedacross the inductance, the capacity of the a condenser being rontrolledby the speed of the :5

vehicle on which the transmitter is located in ,a 1 manner which willhereinafter be explained in detail. The wire l2 from the plate oi tubeII V is connectedto one seem the inductance l0 and wire I3 from the gridof theoscllla'tor connects 30 a inductance connected to the grid thantothe side 35 connected to the plate. "The transmitting anktennae i8 isconnected through the condenser to a point on the inductance l lwhich isremote from the grounded portion thereof; The purpose of thismuchof thecircuit is, when energized, 4

' to generate and transmit radio frequency oscil,

lations. a y t a t It is desirable, however to transmit modulated.

" radio frequency waves. and for this purpose I;

providea modulator vacuum tube 20 which may 45 also be a type '30 triodetube; 1 The plates of both oscillator and modulator tubes receivecurrent i'rom thepositive side of battery 2| throughthe winding 22 oftransformer 23. A radio frequency choke coil is of suitable inductanceis m theline leading from winding 22 to the plate of oscillator 1 tubei0 in order to prevent radio irequencycurrent from'passing into theplate supply or modulator portions of the circuit. Paralleling the l I23 which may have a capacity of .00025 microfarad. One side of thewinding 24 is connected to the grid of the modulator tube 20 and theother side of the winding is connected to the grounded side of thefilament of tube 20. The winding 24 is so connected to the grid andfilament of tube '23 that a sudden increase in current through winding22 will induce a potential difference between grid and filament whichwill be in a direction to still further increase the current demanded bythe plate of tube 20. The number of turns in the windings 22 and 24 maybe in the ratio 10 to 1, respectively. Both tubes l0 and 20 receivefilament current from a suitable battery 26 through a switch 21 whichacts to energize the whole system. The switch 21 -may be operated incon- Junction with the ignition switch of an automobile on which thetransmitter is located, or it may be the ignition switch itself.

The operation of the modulator is then as follows: Assume theoscillator, to be oscillating and transmitting a continuous radio wave'from the antennae, and drawing a certain plate current through thewinding 22. If the plate current of the tube 23 increases, the voltagedrop across the winding 22 increases, decreasing the plate voltage ofthe oscillator tube Hi and reducing the current in the oscillatingcircuit and consequently in the antennae. when the plate current of tube23 decreases, the opposite effect is secured and the radiated powerincreases. Due todifierences of phase in the system, the modulator tubewill oscillate and continually change the plate current through thewinding 22, thus continually changing or modulating the energy radiatedfrom the antennae l3. The capacities and inductances in the modulatorcircuit are adjusted to provide a frequency of modulation preferably inthe audible range in order that a receiving settuned to the carrierradio frequency will emit an audible signal.

It has been stated that the capacity in the oscillating circuit of theoscillator is varied in response to the speed of the vehicle. For thispurpose I employ a plurality of condensers 30, 3|, 32,and 33 each ofwhich has one terminal connectedto wire l3. The other terminal ofcondenser 30 is connected to switch terminal 34; condenser 3| toterminal 35; condenser 32 to terminal 33 and condenser 33 to terminal31. The terminals 34, 35, 33, and 31 are part of a switch 38 which isshown diagrammatically as having a switch arm 33 connected to wire l2and adapted to be swung into connection with any of the ter-' minals 34,33, 33, 31. The switch 38 is controlled by the speed of the vehicle onwhich it is located in such manner that contact is made through terminal34 at a vehicle speed of say, 20 to 35 miles per hour; through terminal35 at, say, 35 to 45 miles per hour; through terminal 33 at, say, 45 to55 miles per hour; and through terminal 31 at speeds above 55 miles perhour. The condensers 33, 3|, 32, and 33 all have substantially differentcapacities which are chosen together with the inductance of coil It sothat the resonant frequency of the transmitting circuit progressivelychanges as the speed changes. Thus condenser 31 maybe of smallercapacity than condenser 30;

condenser 32 of smaller capacity than condenser ,3l;.iand condenser 33of smaller capacity than condenser 32. The constants of the circuit areso chosen that the frequencies of the waves corresponding to differentsp edra'nges are sufllciently separated from one another to assure thatthey can be accurately interpreted even though the constants ofindividual installations may vary here shown diagrammatically, is shownand de-' scribed in my copending patent application, Serial No. 715,049,filed March 12, 1934, which issued as Patent No. 2,117,440 on May 1'1,1938. As disclosed in that patent, a pivoted switch member here showndiagrammatically at 33 is connected with the speedometer mechanism ofthe car along with the usual visible speed-indicating means, and havinga normal path spaced from the series of terminals 34, 35, 33, and 31 sothat the switch member operates in the same freely swinging manner asthe visible indicating means. A cam means driven by the usual odometermechanism of the car intermittently deflects the switch member 33 fromits normal path to close a circuit through whichever of the terminals 41happens to be opposite the switch member, the

particular terminal corresponding to the instant speed of the car. whena circuit is closed by deflection of the switch member 33, it is heldclosed by an automaticlatch that is released by the next operatingmovement of the intermittent means. Thus, if the intermittent means isadjusted to operate at each eighth of a mile of vehicle travel, a signalcircuit closed to indicate a given speed will remain closed for oneeighth of a mile of vehicle travel regardless of any reduction in speedin the course of that eighth of a mile.

By virtue of the switch equipped with a latching means, the signaloccasioned by a speed violation will be prolonged through a substantialinterval of time regardless of whether the violation continues throughsuch interval. This feature favors the apprehension of speed violatorsand discourages any tendency of a driver to engage in a dangerousmomentary burst of speed.

In operation, the practical effect of the use of such a switch in thetransmitting circuit above-described isas follows. If a vehicle havingthis equipment starts down the street from rest and graduallyaccelerates, no-signal is given out until the car has reached 20 milesper hourand the car has gone far enough for the switch to function.Thereupon a modulated radio frequency wave is transmitted and continuesto be transmitted until the car speed exceeds 35 miles per hour. Afterthe switch has again operated, the carrier frequencyof the modulatedwave is increased. When the speed exceeds 45 miles per hour, the carrierfrequency again increases, and when the speed exceeds 55 miles per hourthe carrier frequency is againincreased. After the car has entered agiven speed range and the corresponding frequency has been transmittedthe frequency of the wave remains the same until the'vehiclehas traveleda" suihcient distance to permit the switch to again operate, regardlessof whether the vehicle may have, in the meantime passed into a differentspeed range.

In order'to shorten the high frequencyconcuit by means ofelectro-magnetically operated relay switches controlled by thespeed-controlled switch 33. One terminal of each of the condensers 33,3|, 32, and 33 is connected to the wire I3. The other terminal ofcondenser 33 is con- 1 to it through relay switch through relay switch42; andthe other terminal of condenser 33 through 'relay switch 43. The

electromagnet coils, of the relay switches 40, 4|, 42,: 43 are.connected between one terminal 1 of, the battery 44 and terminals 34,35, 38, and 31, respectivelyfofnthe speed-controlled switch .38. v Theopposingyswitch contact 39 is connected to the other'terminaliof thebattery 44. Thus when the contact. arm :39 is contacting terminal. 34,the coil of relayf40 is energized to hold switch 40 closed and keepcondenser 30 the oscillating, circuit. When the contacting arm .39 movesto;

contactfwith another terminal,v the relay conne ctedthereto operates itsswitch and the switch 40 is opened. ,In this arrangement, as in'thatpreviously, described, the switch 38 is only shown diagrammatically. andis intended to represent the switch disclosed in mycopending-application.

abovereferred to. The remainderof the circuit is ,th same in, structureand operation as that of Fig. 1.,

For receptionof the speedcontrolled radio signal transmitted-by themoving-vehicle, I provide areceiving set suitable for installation inuum tube 52 is alsoconnected. The vacuum tube 52 is preferably 6D6 typeof pentode tube having.

another vehicle, .the electrical circuit of which is shown in Fig- 2. Areceivingantennae 50 is .connected to an inductance 5| ata point nearone end, towhich point the cathode ofthe vacthree grids. The end ofinductance 5i nearest the. point to which the antennae is connected aconnects through conductor, 53 .with one of the wgrids-of tube Hand; isgrounded. I The other end.

ofinductance iiconnects with the control grid 7 of tube 52 throughconductor 54 and condenser II whlchmay be of .00025'microfarad' andwhich 'is shunted by "resistor l6 which 'may be of 5 megohmsresistance.

Across'the inductance ii is connected a tun- .ing: condenser arranged totune the receiving circuit to any 01'. the four frequencies transmittedby'the transmitters of Fig. I or: Fig. 3. Condensers 51, N, 59, and"each have one terminal connected with conductor 54 and the otherterminal connected to terminals ti, 82, 64, and 64. respectively. ofswitch switch 65, adapted to contact any. of the terminals, 62, I3. 64,is connected to the conduc- V esecondensers and the'inductance of thecoil are so adjusted tor ll. The capacities of th that when the switch"arm 68 is on terminal 61,

the set is tuned to receive the signal transmitted T by the circuit ofFig." 1 or Fig. 3 when condenser '30 is connected in its oscillatingcircuit; when condenser 58 is connectedflin' the tuning v circuit theset receives the signal transmitted when condenser 3| is connected inthe oscillating circuit of the transmitter. Likewise when condenser I!or 60 isconnected in the tuning circuit the receiving set receives thesignal transmitted when condenser 32 or n respectively. is in theoscillating circuit of the transmitter. Adjustable trimming condensersmay be employed in parallel with the condensers in the tuning circult.It isdesirable that the tuning of the circuit be rather broad. in orderthat the set will be certain to receive all signals of the frequencywhich is being selected, even if some of the' transmitted waves are notexactly at the frequencies intended. i

other terminal of, condenser 3i throughrelay switch 4i; the otherlterminal of condenser 32 Switch arm 66 of Theplateof tube 52 receivescurrent from the positive side of battery 81 through inductance 68 whichmay be of 500 henries, and through radio frequency choke coil 68.1301169 is shunted by two condensers and H and a lead 12 is connected fromtheir commonpoint to the ground conductor 53. Across the, battery. 81are resistor 13 and potentiometer 14, with] thepoe tentiometer connectedto the negative. [side' of the battery which is grounded. The adjustablearm of the potentiometer i4 is connected to the remaining grid of tube52 and is [connected through condenser I5 13 maybe of- 25,000 ohms, andthe potentiometer 14 of 50,000. ohms, while the condenser may be of .5microiarad capacity. point of connection of coils 68 andBQis connect edthrough condenser 16, of about .ol'microfarad capacity, to the grid ofvacuum tube 11.

which may be a type 42 pentode tube... The grid of tube 11 is alsoconnected by resistor 18 with ground- The cathode to ground through theresistor The plate of tube 11 receives to ground. The resistor Thecommon,

of tube 11 connects. 19, which may be i of 410 ohms and which isparalleled by condensen" which maybe of .5 microfarad capacity.-

current from the positive side of battery through the primary winding ofoutput transformer 8|. "To the sec--, ondary of the output transformerII is connected the head set or loud speaker 82. The heating filamentsof both tubes 52 and 11 are supplied with current from the battery 83through switch 84 which servesto energize the system. One side or thebattery 83 is grounded. 1

In operation, the system performs as follows.

The transmitter of Fig. 1 or Fig. 3 being located on the moving vehicle,automatically transmits,

explained above, a modulatedradio frequency speed of the vehicle. Thereceivingset of Fig. 2 may be located on a police vehicle patrolling inthe section near the transmitting vehicle. a If the speed limit is milesper 'hour in that vicinity, the police oflicer operating the receivingset would likely adjust switch so that condenser 58 is in the tuningcircuit. In this case. when the speed of the transmitting vehicleexceeds 35 miles per hour, awave is transmitted having a radio frequencyto which the receiving set is wave of a carrier frequency dependentuponthe.

It will be seen that this system provides law enforcement oflicers witha very eflective'means for policing vehicles. As motor cars arecontinually becoming faster and more powerful and are more widely usedby the public, the importance of the invention is easily appreciated.

While I have described my apparatus as operating at certain definitementioned speeds. it will, of course, be understood that itflmay be madeto operate at any chosen speeds or in any number oi steps. I haveillustrated my invention by use of a specific transmitting circuit andreceiving circuit, but obviously any of the many suitable transmittingand receiving circuits known in the radio art can be employed topractice my invention. Instead of an audible signal from a loud speaker,any other sensible signal such as a light 78 may be employed inconnection with the receiv- 1 ing set. These and any other changes andmodiflcations which may be made by those skilled in the art are intended.to be included as a part of my invention so long as they are within thevehicle adapted in response to the speed of said. vehicle to change theradio frequency of the as sociated transmitter to said given frequencywhen the vehicle travels in the corresponding prohibited range of speed.I

In a system for policing a plurality of vehicles in tramc, thecombination or: a radio re-' ceiving station tuned to a given radiofrequency frepresentative of a prohibited speed; a radio the tuningcircuit of the associated transmitter;

transmitter on each or said vehicles; a modulator incorporated in eachof said transmitters adapted to modulate the transmitted waves at asignal frequency; a condenser oi fixed capacity associated with each ofsaid transmitters and adapted to tune the transmitter to said givenradio frequency; a switch associated with each of said condensers toconnect the condenser in and means on each vehicle for connection withthe speed indicating mechanism of thewehicle and adapted to operate saidswitch, thereby to connect said condenser in the tuning circuit of thetransmitter when the vehicle travels at said prohibited speed.

3. In a system Ior policing a plurality oi! vehicles in trafilc, thecombination of: a radio receiving station adapted to be tuned topredetermined frequencies representative of prohibited ranges of speed;a radio transmitter on each of saidvehicles modulated to produce asignal or distinctive character at said receiving station; a plurality01' radio frequency tuning condensers associated with each of said radiotransmitters or fixed capacities corresponding to said prohibited rangesoi speed; and a switch on each vehicle for connection with the speedindicating mechanism of the vehicle to operate in the prohibited speedranges to connect in the tuning circuit of the associated radiotransmitter that one of the condensers that corresponds to the instantspeed of the vehicle.

4. In a system for policing trafllc, the method of automaticallyindicating by a radio receiver at a traflic-supervision station speedviolations among a plurality of vehicles, said method comprising:transmitting a radio signal from each or said vehicles when the vehicletravels at a prohibited speed; tuning said signal to a predeterminedvalue indicative of the prohibited speed;

and tuning said receiver to be selectively responsive to said valuerepresenting the prohibited speed, whereby said receiver will functionas an automatic alarm to indicate speed violations.

5. In a system for policing traiilc, the method of automaticallyindicating'by a radio receiver at a ti anic-supervision station speedviolations 7 among a plurality of vehicles, said method comprising:transmitting a radio signal from each of said vehicles when the vehicletravels at aprohibited speed; tuning said signal to a predeterminedvalue indicative oi. the prohibited speed; tuning said receiver to beselectively responsive to said value representing the prohibited speed,

whereby "said receiver will automatically signal the tramc violation;and continuing said radio signal from-the vehicle for a predeterminedinterval independently or any change in speed of the vehicle.

6. In a system for policing aplurality 0! vehicles in traflic, thecombination of: a radio receiving station tuned to a given radiofrequency representative of a prohibited'range 0! speed; a"

radio transmitter on each or said vehicles modulated to produce a signalof distinctive character at said receiving station; a radio frequencycontrol' for said transmitter adapted to move into and out oi a settingat said given irequency; and means for connection with the speedindicating mechanism of each vehicle to move said control into and'outof said setting accordingto whether the vehicle travels in or out ofsaid prohibited range of speed, said means being adapted to hold saidsetting for predetermined intervals of dis tance in the travel of thevehicle.

'7. In a system for policing a plurality 0! vehicles in tramc, themethod of indicating by means of a radio receiver at a tunic-supervisionstation violations of speed laws by any'or'said' vehicles, said methodcomprising: transmitting a radio signal for a predetermined intervalfrom any one of said vehicles whenever said vehicle enters-a prohibitedspeed range; and tuning said receiver to be selectively responsive tosaid signal representing the prohibited speed, whereby said receiverwill automatically give a signal for said predetermined minimum intervalwhenever one of the vehicles operates at the prohibited speed.

-8. In a system for policing a plurality oi! ve-, hicles in trafllc, themethod 01 indicating by means of a radio receiver at atraffic-supervision station violations of speed laws by any one of saidvehicles, said method comprising: transmitting a radio signal-from eachof said vehicles; periodically changing the tuning of said signal to avalue corresponding to the speed range in which the vehicle ismomentarily traveling; and tuning said receiver to beselectivelyresponsive to a value representing a prohibited speed.

Donald) E.

